Electric arc melting furnace



Sept 16, 1958 G. A. slxl-:L 2,852,585

ELECTRIC ARC MEILTING FURNACE .fm/ewan' Sept-16.1958 G. AfslxEL 2,852,585

ELECTRIC ARC MELTING FURNACE Filed April 15, 1957 '2 Sheets-Sheet 2 United States Patent C ELECTRIC ARC MELTING FURNACE` f Gustav Adolf Sixel, Dusseldorf-Kaiserswerth, Germany, assignor to Aktiengesellschaft fuer Unternehmunger der Eisenyund Stahlndustrie, Essen, Germany Application April 15, 1957, Serial No. 652,955 l Claims priority, application Germany May 9, 1956 8 Claims. (Cl. 13-10) Electric arc melting furnaces,` as they are commonly used in the vproduction of steel, employ electrodes operating at low voltages so that they have to be connected to the high power lines via a transformer. In case of larger furnace units, the current densities become very high. This makes it diicult to provide low-loss connections of the necessary exible conductors between the transformer and the terminals of the electrodes.

These known melting furnaces must be made movable to permit discharging of the molten metal or charging of the scrap metal. However, in the past, the associated transformers have not taken part in the furnace movements, said transformers being separate and stationary with respect to the adjacent furnaces. The positions of the connection terminals of the electrodes are considerably displaced during furnace movement with respect to the connections at the stationary transformers when the furnace is moved, as indicated in the foregoing. As a result of this, relatively long connecting conductors have to be provided between the electrode and transformer terminals. Such long connecting conductors, which are mostly of copper, tend to sag to a great extent and are, therefore, very inconvenient and tend to have great current losses.

In order to decrease the length of these conductors, electric arc melting furnaces have been designed in such a manner, that the electrodes and thus their terminals do not take part in the displacements of the furnaces, for example, in the tilting movements. However, even in such construction, the minimum electrical length of the conductors necessary for connecting the transformer to the electrode terminals would be too short to permit the furnace cover to be removed or turned by means of its carrying frame when recharging the furnace with scrap metal. During such operations, the conductor connections at the transformer and those at the electrode terminals are moved away from one another, so that greater conductor lengths become necessary.

It is a primary object of the present invention to avoid long connecting conductors such as have been heretofore necessary to permit turning or removing of the furnace cover during the recharging.

It is another object of the invention to place the transformer on the furnace cover supporting frame which includes the electrodes, so that the transformer takes part in all turning or displacing movements of the cover supporting frame. As a result of such structure, the connecting conductors between transformer and electrode terminals can be made of minimum length, so that these conductors scarcely sag and are short enough to have low electrical losses and satisfactory mechanical stability.

It is a further object of the present invention to pass the feed lines from the high voltage power lines to the primary of the transformer through a hollow pivot about which the cover supporting frame is rotatably mounted.

Still further objects and the entire scope of applicability of the present invention will become apparent from the ice detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples;'whileindictating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

In the drawings:

Figure 1 is a side elevation of an electric arc furnace and associated transformer according to the invention;

Figure 2 is a plan view of the electric arc furnace and transformer of Figure 1, but with the furnace cover shown in displaced position for recharging;

Figures 3 and 4 show partial vertical enlarged sections taken in two planes perpendicular with respect to one another and passing through a modified cover supporting frame at its pivot, according to an object of the present invention, and wherein Figure 3 is a section taken along line III- III of Figure 4 and looking in the direction of the arrows. p

Referring in more detail to the drawings, Figure l shows a furnace body a open at the top and mounted on rocking cradles b in a manner known per se. Electrodes c1, cl2 and c3, carrying terminals d1, d2 and d3, respectively, are mounted in and passed through a cover g seated on the open top of the furnace body a.

A cover supporting frame e carries the cover g with the electrodes c1, c2 and c3 and their clamps or terminals d1, d2 and d3, i. e., this cover g is suspended from an upper arm e1 of the frame e overlying the cover g by means of cables indicated at f1 and f2. When the furnace is to be charged, sectors f1 and f2 to which these cables at f1 and f2 are respectively attached will lift the cover g when the sectors l and f2 are turned in the direction of the arrows by means of a drive mechanism (not shown). The supporting frame e rests on rollers /z running on a stationary track i disposed in a circular arc. The supporting frame e rotates about a fixed pivot k, about which this frame e can be turned or swung to the position shown in Figure 2 by means of a drive mechanism l.

A transformer m is mounted on a platform e2 of the cover supporting frame e and the secondary of this transformer is connected to the terminals d1, d2 and d3 of the electrodes c1, c2 and c3 by means of conductors n1, n2 and n3. The terminals of the primary of the transformer m are connected to the high voltage power lines (not shown) by means of lines or bus bars x, y, z.

In order to permit limited displacement of the feed lines to the primary of the transform m from the power lines during the turning of the frame e, these feed lines are passed through a hollow pivot k, as shown in the modied embodiment of Figures 3 and 4. The part of the feed lines passing through the hollow pivot k' which is mounted on the iloor by means of a foot k1 constitutes the end portion of a high voltage cable q connected to the supply power lines (not shown). This cable q enters the hollow pivot k' from an underground duct r through which the cable q is passed. The cable q ends in a cable head t just outside and above the top of the pivot k', from which the three phases emerge as bare conductors x, y and z. Insulators p1, p2 and p3 mounted above the upper end of the hollow pivot k by means of a bracket o support the bare conductors x, y and z close to their ends where they emerge from the cable head I. Two spaced sets of insulators u1, u2 and M3 and ul, u'z and 153, secured to a bracket or vertical extension w of the carrying frame e at the right side thereof, serve as further spacers for the bare conductors x, y and z, ending at the high voltage terminals on top of the transformer m (see Figure l). Since the insulators u1, u2, us, u'1, u2 and u3 are subjected to a turning movement of about 30 of the frame e, portions v1, v2, v3 of the conductors x, y and z between the insulators p1, p2 and p3 and the insulators u1, u2, ua have to be made flexible to permit the necessary displacements.

In certain types of furnaces, the. frame e' maybe displaced linearly rather than rotationally andinfsuch case, maybe designed in the form of a gantry. However, the construction illustrated in Figures l and 2 of theV drawing has the advantage that the access to the furnace is cluttered only at one side thereof by the cover supporting frame. y

I claim:

1. An arc melting furnace supplied with electrical energy from a power line, comprising a melting vessel open at, its top, la cover removably seated on said-top at least one electrode mountedin said cover, a cover-supporting frame carrying said cover and said associated electrode when said cover is unseated from said top, means to displace said supporting frame with respect to said melting vessel to uncover the latter, a power transformer supply-V ing the electric energy and having a primary connected to said power line, said transformer being mounted on said supporting frame, and electric conductor means connected between the secondary of said transformer and to permit turning movements of said frame with respect,

to said melting vessel.

.wherein said cover is suspended from said supporting frame by means of exible members adapted to lift said cover from said melting vessel.

4. An electric arc melting furnace according to claim 3, wherein said supporting frame has an arm overlying said cover, said flexible members being suspended from said arm.

5. An electric are melting furnace according to claim l, wherein said supporting frame has a platform on which said transformer is mounted.

6. An electric are melting furnace according to claim 5, wherein said` platform is adjacent the axis of said pivot.

7. An electric arc melting furnace according to claim 6, wherein astationary track in an arc about the axis of said pivot is provided and wherein rollers are rotatably mounted on the bottom of said supporting frame to roll on said track, said platform being disposed between said track and said rollers.

8. An electric areV melting furnace according to claim 2, whereiny said pivot is hollow andy the feed lines to said' primary of said transformer are passed through said pivot.

References Cited in the le of this patent y UNITED STATES PATENTS Re.16,054 Moore 1 Apr. 28, 1925 2,396,663- v Kuelthauet al Mar. 19, 1946 UNITED STATES PATENT oTiFTCE CERTIFICATE GF CQRRECTION Patent Noa 2,852,585 September 16, 1958 Gustav Adolf Sixel I ItI is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected belowo In the grant, lines 2 and l2, and in the heading to the printed specification, line 4, for "Unternehmunger" read Unternehmungen in each occurrence.

signed and Sealed this 13th day of January 1959u (SEAL) Attest:

KARL H., AXLINE ROBERT C WATSON ttesbing Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noa 2,852,585 September 16, 1958 Gustav Adolf Sixel It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below In the grant lines 2 and l2, and in the heading to the printed specification, line 4, for "Unternehmunger" read Unternehmungen in each occurrence.,

signed and Sealed this 13th day of January 1959u (SEAL) Attest:

KARL H., AXLINE ROBERT C. WATSON Attestlng Offlcer Cmnissioner of Patents 

